It’s certainly possible to create an app with that same functionality and host it on the HubSpot COS, but I’m not able to consult on the exact implementation. The link I provided was intended as a reference, not a guide. I’d be happy to answer any HubSpot specific questions, but you’ll need to create the color tool on your own.
Thank you for suggestion but I want to showcase these following elements as in the link shared by me-
Pencil
Paint Brush
Marker
Water Color
Eraser
Undo
Restart
Select SVG